Dynamic optimization of countercurrent heat exchangers with phase change

JUAN I. LAIGLECIA; PATRICIA HOCH; MARIA SOLEDAD DIAZ

Chemical Engineering Greetings to Prof. Sauro Pierucci

AIDIC, Italian Association of Chemical Engineers

Lugar: Milán; Año: 2011; p. 185 - 192

This paper addresses dynamic optimization of shell and tube countercurrent heat exchangers with phase change, through first principles mathematical models, within a simultaneous approach. Partial condensation of natural gas takes place on the shell side. Dynamic mass, energy and momentum balances are formulated for the condensing fluid. The resulting distributed parameter problem is transformed into a lumped parameter one by applying the method of Lines for the spatial coordinate. Additional constraints to prevent temperatures crosses and to ensure spatial temperature monotonicity are directly handled as path constraints within the simultaneous dynamic optimization approach. The differential algebraic equation system is transformed into a large nonlinear programming problem through orthogonal collocation over finite elements in time and solved with an interior point algorithm. The model provides temporal and spatial profiles of control and state variables that are in good agreement with plant data.